1. Field of the Invention
The disclosed and claimed concept relates generally to electrical switching apparatus and, more particularly, to a housing assembly for an electrical switching apparatus wherein a movable door provides access to a vault.
2. Background Information
Electrical switching apparatus include, for example, circuit switching devices, circuit interrupters, such as circuit breakers, network protectors, contactors, motor starters, motor controllers, and other load controllers. Electrical switching apparatus such as circuit interrupters and, in particular, circuit breakers of the molded case variety, are well known in the art. Circuit breakers are used to protect electrical circuitry from damage due to an over current condition, such as an overload condition or a relatively high level short circuit or fault condition. Molded case circuit breakers typically include a pair of separable contacts per phase. The separable contacts may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to an over current condition.
In an exemplary embodiment, circuit breakers include an operating mechanism, which is designed to rapidly open and close the separable contacts, a trip unit, which senses over current conditions, and a trip actuator assembly. The trip actuator is actuated by the trip unit in response to an over current condition and moves the operating mechanism to a trip state. In the trip state the separable contacts move to their open position.
The electrical switching apparatus housing assembly includes a non-conductive body, e.g. the “molded case” noted above. The housing assembly includes a base member and a cover member or assembly. The base member defines a number of cavities into which the other components are disposed. The base member is coupled to either the cover member or the cover assembly thereby substantially enclosing the components. A cover member is a generally planar member that covers the entire base member. A cover assembly includes a thicker body that also defines a number of cavities. The cover assembly body may be a unitary body, or, the cover assembly may further include a planar cover member that is coupled to the cover assembly body. Cover members and cover assemblies generally have the same cross-sectional area as the base member. In this configuration, accessing the housing assembly enclosed space required the user to separate the base member and the cover assembly, or cover member, thereby exposing the entire enclosed space to infiltration by dirt and debris.
It is also known to provide accessory components for an electrical switching apparatus. An accessory component is coupled to the operating mechanism or trip unit. An accessory component is disposed in a cavity, also identified as a vault, within the cover assembly body. To access the vault a user would either have to remove a cover member or a smaller vault door. As noted above, removal of a cover member opened the entire cover assembly body cavity. A door, while smaller than a cover member, was typically disposed over the vault as opposed to in the limited opening associated with the vault. For example, the door was a planar member that pivoted between an open position and a closed position. Such doors are prone to open during a trip event or fault interruption event. That is, during a trip event, an arc may heat the air and adjacent breaker components causing a rapid expansion of gas in the housing assembly enclosed space. The rapid expansion of the gas caused the pivoting doors to open, thereby exposing the vault.
There is, therefore, a need for a vault door member that is disposed in the limited opening and which is resistant to unintentional opening. There is a further need for such a door member to be easily incorporated into existing housing assembly configurations.